Raypak 910500, Owner'S Manual And Installation Instructions

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Flow Switch
The flow switch is mounted in the outlet of the water header and is
wired via a self-proving relay in accordance with AS 3814. It will
prevent the heater from operating in the case of pump failure or low
water flow. (
see Fig. 49 )
Fig 49: Flow Switch
Blocked Flue Switch
The blocked flue pressure switch (smaller of the two
pressure switches) prevents the operation of the heater
when too much of the flue is blocked. This switch is
located on the right side of the heater near the right rear
corner. (see
Fig. 50 )
Fig. 50: Blocked Flue Switch
Air Pressure Switch
This heater is equipped with an air pressure switch (larger of
the two pressure switches) to ensure the fan is operating
before entering ignition mode in accordance with AS 3814. It
operates during pre-purge, ignition sequences and all stages
of normal burner operation. This switch is located on the right
side of the heater near the right rear corner. (see
Fig. 51 )
Fig. 51: Air Pressure Switch